Steering systems of certain motor vehicles, such as racecars, demolition derby cars and off-road vehicles, include a direct link between a steering wheel and wheels. The steering wheel is rigidly secured to a steering column. The steering column is connected to a mechanism that translates rotational motion of the steering wheel into a turning motion of the wheels. In one embodiment, the mechanism includes tie rods attach directly to the steering column. Each tie rod is connected to one of the wheels. Turning the steering wheel rotates the steering column and translates the tie rods in opposite directions, thereby moving the wheels in the intended direction.
Advantageously, this system is simple, inexpensive, easily repaired, and affords positive steering feedback to the driver. But this system does include a major shortcoming. While any movement of the steering wheel will induce movement in the wheels, the inverse is also true, that is, movement of the wheels will cause the steering wheel to turn. Motor vehicles can travel at high speeds. The wheels impacting a curb or other obstruction at high speed can cause the steering wheel to rotate violently.
Drivers tend to grip tightly the steering wheel, especially at high speed. A sudden violent rotation of the steering wheel contains enough energy to injure the driver. Injuries include broken bones, especially the wrists and thumbs, sprains, contusions and bruising. Even if the driver escapes injury, the sudden movement of the steering wheel can cause the driver to lose control of the vehicle at least temporarily.
Previous attempts to overcome this problem include the installation of power steering systems, electronic torque converters, and breakaway mechanical linkages. Power steering systems add significant complexity and weight to the steering system and reduce, but do not eliminate, the risk. Electronic systems can be effective, but are expensive, difficult to install, and subject to breakdown. Breakaway linkages include gear or pin mechanisms that are designed to disengage or shear at excessive torque. Unfortunately, this leads to at least a temporary loss in steering control.
An object of this invention is to provide a simple device that passively controls violent rotation of a steering wheel when the wheels impact an obstacle, thereby reducing injury to the driver. The invention should also at all times retain positive steering feel and control.